Vehicle-to-X communication, also known as C2X communication, based on IEEE 802.11p, ITS-G5 or IEEE 1609, is the prior art and standardized, and has already been tested in field tests. This technology makes it possible for messages to be exchanged between vehicles which, in turn, makes it possible to notify drivers about possible hazardous situations. The creation time of the respective message is also sent in such messages and is used or filtered by other subscribers.
In order to prevent abuse, the relevant messages are typically signed with certificates and the validity thereof is checked by means of a certificate chain in a control unit. However, these certificates are only valid at certain times.
According to the prior art, a satellite navigation receiver is typically used, for example a GPS receiver, in order to record a time. This time is used throughout the system for synchronization purposes. However, there is a potential threat to the system in that a hacker can reproduce the vehicle environment (for example, satellite navigation signals and vehicle interface, etc.) and generate artificial warning messages or messages for any time and any place. Such artificial messages (for example, emergency brake, traffic jam ahead) can then be recorded and played back at sensitive infrastructure points such as, for example, motorway junctions. This could lead to significant disruptions and pose a hazard to road traffic.
In addition, certificates stored in the control unit could be set to invalid, for example by means of an artificially simulated incorrect time. The control unit can therefore be permanently decommissioned.
It is true that it is in principle possible to supply a clock with power by means of a permanent power supply even in the switched-off state. However, a plausibility check is not always possible due to an interruption in the power supply, which corresponds, for example, to the normal operating condition in a workshop.
As such, it is desirable to present a device for monitoring the time during an interruption period, which makes it possible to carry out plausibility checks of times independently of a power supply. It is, in addition, also desirable to provide a vehicle-to-X communication module having such a device. In addition, other desirable features and characteristics will become apparent from the subsequent summary and detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.